Organosiloxane copolymers



United States Patent Ofiice I 3,334,120 Patented Aug. 1, 1967 3,334,120 ORGANOSILOXANE COPOLYMERS George W. Holbrook and Harry M. Schiefer, Midland,

Mich., assignors to Dow Corning Corporation, Midland, Mich., a corporation of Michigan No Drawing. Filed June 10, 1963, Ser. No. 286,491 10 Claims. (Cl. 260-4482) This application is a continuation-in-part of applicants abandoned application Ser. No. 281,032, filed May 16, 1963 entitled, Siloxane Copolymers.

This invention relates to organosiloxane copolymers containing halophenylsiloxane units and fluoroalkylsiloxane units which copolymers are particularly useful as lubricants and hydraulic fluids.

With the commercial advent of hydrocarbon substituted organosiloxanes it soon became apparent that these materials, particularly the methylsiloxanes, had many of the desirable properties required for lubricants operating over a wide range of temperature. These properties were: excellent high temperature stability, extremely low freezing point and a relatively slight change in viscosity with temperature. However, the hydrocarbon substituted siloxanes suffer from one serious defect; namely, that they were not satisfactory lubricants for sliding steel on steel bearing surfaces. Since steel is the primary metal employed in machinery the use of hydrocarbon substituted siloxanes as lubricants has been severely restricted.

The first major improvement in siloxane lubricants came with the introduction of halophenylsiloxanes such as those described in U.S. Patent 2,599,984. It was found that by incorporating halophenylsiloxane units into hydrocarbon substituted siloxanes one could greatly improve the lubricating quality of siloxanes. However, the improvement was not sufficiently good tomake these materials generally satisfactory for the lubrication of steel sliding surfaces.

An even greater advance came with the introduction of fluoroalkyl'substituted siloxanes such as trifluoropropylmethylsiloxane. Homopolymers of these materials are excellent lubricants for sliding steel on steel bearing surfaces and in most respects they are equivalent to the best hydrocarbon oils. However, the fluoroalkylsiloxanes sulfer from the serious disadvantages that they have a relatively steep temperature viscosity slope and are not useable as lubricants at temperatures below 40 F. or as an aircraft hydraulic fluid below F. Thus, fluoroalkylsiloxane homopolymer fluids are not useable as lubricants in a wide variety of applications which require that the lubricant function at low temperatures. As a result, there is a great'need for a material which has the desirable high temperature stability and lubricating qualities of the fluoroalkylsiloxanes while also possessing excellent low temperature stability so as to enable one to use the fluids at low temperatures.

Attempts have been made to obtain this result by copolymerizing the fluoroalkylsiloxanes with methylsiloxanes. These copolymers do indeed have low temperature properties in that they remain fluid at temperatures below 65 F. However, the lubricating qualities of such copolymers are poorer than the fluoroalkyl homopolymers. Consequently, such copolymers are not the answer to the problem posed in this invention. 7

Applicants have found most unexpectedly that copolymers containing both fiuoroalkylsiloxane units and halophenylsiloxane units as defined below have lubricating properties approaching, or better than, those of the fluoroalkyl homopolymers but still will operate at extremely low temperatures. Thus, the fluids of this invention fill a long standing need in the silicone lubricating art.

This invention relates to copolymers having (1) units of the group and R SiO on the ends of the molecules, the remaining units in said copolymer being substantially all (2) units of the group consisting of (a) R'SiO and | I si 810 the total units (2) being present in amount of at least 24 mol percent of the total copolymer and any units (b) being present in amount from 0 to 25 mol percent of the amount of units (a) and in the amount of 0 to 15 mol percent of the total copolymer,

( nGZn'H R Q HOH2SiO units in amount of at least 5 mol percent of the total copolymer,

units in amount such that the total number of units of H the formula Mes in said copolymer is from 1 to 15 mol percent of the total copolymer, and

(5) ZSiO units in amount of from 0 to 10 inclusive mol percent, said units being interconnected through SiOSi linkages in which R is of the group methyl, phenyl, and

Q is of the group hydrogen and C F CH CH n is an integer from 1 to 8 inclusive,

R and D are each of the group methyl and phenyl radicals, at least one R and D per silicon being on the average -a methyl radical,

R' is of the group phenyl and methyl radicals,

Z is of the group phenyl, methyl and Q HCHrradicals,

X is of the group chlorine and bromine,

' a is an integer from 1 to 4 inclusive, and

b has a value from 0 to 2 inclusive.

groups such as trifluoropropyl, penta- It should be understood that any combination of these groups can be attached to the silicon of the triorganosiloxy group (1). In addition (1) can be any suit of the formula Thus, specific examples of triorganosiloxy groups are trimethylsiloxy, triphenylsiloxy, phenyldimethylsiloxy, tribromophenyldimethylsiloxy, tetrachlor-ophenyldimethylsiloxy, monobromophenyldimethylsiloxy, trifluoropropyldimethylsiloxy, bistrifiuoropropylmethylsiloxy and a CF CHzCH2CHCH:-

dimethylsiloxy.

The substituents (2) can be entirely dihydrocarbonsiloxy groups (a) in which the substituents are phenyl and methyl radicals or (2) can be made up of up to 25 mol percent based on the amount of (a) of (b) silphenylene units of the formula in which D is phenyl or methyl. The total amount of silphenylene units, however, should not exceed 15 mol percent of the total copolymer. In all cases there should be an average of at least one methyl group per silicon atom in the total number of (2) units. Thus, (2) can be made up entirely of dimethylsiloxy units or of phenylmethylsiloxy units or any combination of these or (2) can be made up of combinations of dimethylsiloxy units and diphenylsiloxy units,

on Me; CqHs CaH Me Me (0 115): MB: e m

( e 5)2 l l s1 s 81 SlO units or (2) can be a combination of phenylmethylsiloxy units with lllleg I l/leg Lite; Ill l6 It should be understood that the copolymers can contain any combination of these fiuoroalkylsiloxane units. Thus, for example, the copolymer can contain both trifluoropropylmethylsiloxane units and pentafluorobutylmethylsilonxane units or the copolymer can contain both trifluoropropylmethylsiloxane units and trifiuoropropylphenylsiloxane units.

One of the essential ingredients of the instant copolymers are the halophenylsiloxy groups. These must be present in amount from 1 to 15 mol percent of the total copolymer. These groups can be of three types, namely,

The latter type of unit is also an endblocking unit (1) and if such units are present in amount to give a total of at least one mol percent halophenylsiloxy units in the copolymers, no additional halophenyl units are needed. However, if desired a combination of any two or all three types of halophenyl units can be present in the copolymer. Thus, the halophenyl units can be located solely on the ends of the molecules or they can be located along the molecular chain of the copolymer or they can be located in both positions in any particular copolymer.

Specific examples of operative halophenylsiloxy units, in addition to those shown under (1) above, are chlorophenylsiloxy units, dibromophenylmethylsiloxy units, tetrachlorophenylmethylsiloxy units, chlorodibromophenylsiloxy units, and tetrabromophenylsiloxy units.

The copolymers of this invention can also contain an optional ingredient (5) which is either monomethylsiloxane units, monophenylsiloxane units, or any CnFfinH Q nomsiom unit where Q and n are as defined above or any combination of these three types of units. Thus (5) can be CF CH CH SiO C F CH CH SiO i CFaCHzCHgUHCHzSiOa/I and In any event, siloxane units (5) should not exceed a total of 10 mol percent of the copolymer.

The copolymers of this invention are best prepared by cohydrolyzing the corresponding chlorosilanes followed by equilibration of the cohydrolyzate with alkali metal hydroxide catalysts or catalysts comprising the alkali metal salts of silanols. During the equilibration it is often desirable to remove water as it is formed and to maintain the equilibrating system in an anhydrous condition. This is particularly true where the halophenyl substituents contain more than two halogen atoms. Thus, it can be seen that the copolymers of this invention are prepared by conventional techniques for copolymerizing siloxanes.

When silphenylene units are to be incorporated into the copolymer it is best to add the corresponding diol of the formula to the acid free hydrolyzate containing the remaining ingredients and to equilibrate the mixture with the alkaline catalysts supra.

The starting halosilanes and diols from which the copolymers of this invention are prepared are all wellknown materials.

The molecular size of the copolymers of this invention is not critical since they are all excellent lubricants regardless of polymer size. However, in many applications it is preferred that the viscosity of the copolymer be in the range for from 25 to 10,000 cs. at 77 F. The copolymers of this invention are particularly desirable for use as hydraulic fluids and for this use a particularly desirable form has a viscosity from 50 to cs. at 77 F. It is obvious that the viscosity of the copolymer will be determined by the mol ratio of triorganosiloxy groups to the other siloxy groups. Thus, the viscosity can be varied at will by increasing or decreasing the mol percent of triorganisiloxy groups in the system.

6 l of the chlorosilane mixture, the product was heated for 15 min. and cooled. About one liter of toluene was added and the organic phase was separated and washed with sodium bicarbonate solution until the toluene solution The compositions shown in the following examples 5 was neutral. were tested for lubricity on the Shell four-ball wear 5 g. of KOH was added and the toluene was removed testing machine. In this test, a /2 inch steel ball is roby distillation. The residue was heated and stirred for tated against three stationary /2 inch steel balls at a 16 hours at 160 to 170 C. 10 g. of Me SiCl was then rate of 1,200 r.p.m. at a temperature of 167 F. under added to neutralize the alkali and the product was then loads of 4, 10 or 40 kilograms for 2 hours. At the end of 10 filtered and heated to 270 C. at .25 mm. under a slow this time the length and width of the scar formed on each N purge and then heated to 275 C. at 2 mm. under a stationary ball is determined and the average of these vigorous N purge. The residue was then heated on a six measurements is taken as the scar diameter and resteam bath for two hours for 5 g. of Na CO and then ported in millimeters. The smaller the scar diameter, the filtered. better the lubricant. 15 The Shell 4-ball wear tests were run at 167 F.

TABLE I Composition of copolymer in mol percent Viscosity in cs. Scar Diameter mm. Run N o. M m

e Mso ClOHSiO Mslo 7F 122F. 210F. 6F 4k. 40k. 83 1 1/2 2 6 a 3/2 62 3OHa Z Sli 7 g g The following examples are illustrative only and should Example 3 not be construed as limiting the invention which is properly delineated in the appended claims. In the specifica- E I11P10Y1I1g the Procedure Example a copolymer tion and claims the abbreviation Me is employed for the havmg the fOlIOWlIlg COmPOSItIOH s Obtalnedmethyl radical. Me

Example 1 CF CH CH SL0 M01 per 651 16 1000 g. of a copolymer of 6.2 mol percent dichlorocgg f, 2 phenylsiloxane, 75.3 mol percent dimethylsiloxane, 13.5 M61810 65 mol percent trimethylsiloxane and 5 mol percent phenyland methylsiloxane was mixed with 200 g. of Me omonroms io 2n (oFioHwHsioh The copolymer was a fluid having good low temperaalld 10 of KOH and the mixture Was Stirred and healed ture stability and excellent lubricity for steel on steel for 18 hours at 160 to 170 C. The resulting fluid was bearing surfaces. neutralized with Me SiCl, filtered and the volatiles were removed by heating to 255 C. at 1 mm. The resulting Example 4 copolymer had the average composition: 5.6 mol percent E l i th procedure of E l 2, a copolymer dichlofophellyl 3/2 11101 p M62510, was obtained having the following composition. mol percent Me SiO 4.9 mol percent C H (Me)S1O M01 per cent and 9.7 mol percent CF CH CH (Me)SiO. Me Si0 4 10 This copolymer had the following propertlesz i gg giasiom 2 Temperature, F.: Viscosity, cs. and

5 4,990 Me 4 77 82.5 I 122 49 1 0 CFQCHflCHISiO 2fl (P011r P The copolymer was a fluid having good low tempera-- ture ro erties and was an excellent lubricant for steel. The fluid was tested on the Shell 4-bal1 wear tester p p and gave a scar diameter of .16 mm. after 2 hours at Example 5 v 1200 -P- at K under a load of 4 65 Employing the procedure of Example 2, a copolymer was obtained having a viscosity of 70.1 cs. at 77 F. and Example 2 having the composition A series of fluids were made and tested as shown in the M01 per cent table below. In each case a mixture of Me SiCl, Me S1Cl 0 2 0 111510. g Cl C -H SiCl and 114510131.-- 11 6 Me 012M016) s10 4.0 omomomsiioh and in the ratios needed to give the compositions shown below, was added to 2850 g. of water. Following addition aGHzCHzOHOHzSiO 13 3 e 500 ml. of toluene and 10 g. of KOH were addedand mixture was heated and stirred as the toluene was distilled. When the mixture was toluene-free the copolymer was heated and stirred for 16 hours at 160 to 170 C. The fluid was cooled and neutralized with Me SiCl, filtered and stripped to 290 C. at 1.5 mm. The resulting fluid copolymer had the composition 10 mol percent Me SiO 5 mol percent C12 Sloan 55 mol percent Me SiO, 15 mol percent Me CF CHgCHiS iO and 15 mol percent It gave a scar diameter of .333 mm. when tested on the Shell 4-ball wear tester at 167 F. for 2 hours at 10 kg.

That which is claimed is: 1. As a lubricant a copolymer having (1 units of the group consisting of and R SiO on the ends of the molecules, the remaining units in said copolymer being substantially all (2) units of the group consisting of (a) R SiO and (b) D2 D2 total copolymer,

units in amount such that the total number of units of the formula Men in said copolymer is from 1 to 15 mol percent of the total copolymer and ZSiO units in amount of from 0 to inclusive mol percent of the total copolymer, said units being interconnected through SiOSi linkages, in which R is selected from the group phenyl, methyl and radicals,

Q is selected from the group consisting of hydrogen and C F2 +1CH2CH2,

n is an integer from 1 to 8 inclusive,

R and D are each independently selected from the group consisting of phenyl and methyl radicals, at least one R and D group per silicon being on the average a methyl radical,

R is selected from the group consisting of methyl and phenyl radicals,

Z is selected from the group consisting of phenyl,

methyl and radicals,

X is selected from the group consisting of chlorine and bromine,

a is an integer from 1 to 4 inclusive, and

b has a value from 0 to 2 inclusive.

2. As a lubricant a copolymer in accordance with claim 1 having a viscosity of 50 to 10,000 cs. at 77 F.

3. As a lubricant a copolymer in accordance with claim 1 having a viscosity of from 50 to cs. at 77 F.

4. As a lubricant a copolymer having (1) trime-thylsiloxy uni-ts on the ends of the molecules,

the remaining units in said copolymer being substantially all (2) dimethylsiloxy units in amount of at least 24 percent,

(3) 3,3,3-trifluoropropylmethylsiloxane units in amount of at least 5 mol percent and (4) dichlorophenylsiloxane units in amount of from 1 to 15 mol percent.

5. As a lubricant a composition in accordance with claim 4 having a viscosity of from 25 to 10,000 cs. at 77 F.

6. As a lubricant a composition in accordance with claim 4 having a viscosity of from 50 to 150 cs. at 77 F.

7. As a lubricant a copolymer having (1) trimethylsiloxy units on the ends of the molecules,

the remaining units in said copolymer being substantially all (2) dirnethylsil-oxy units in amount of at least 24 mol percent of the total copolymer,

mol

Mei Mei and R SiO on the ends of the molecules, the remaining units in said copolymer being substantially all (2) units of the group consisting of (a) R' SiO and the total units (2) being present in amount of at least 24 mol percent of the total copolymer and any units (b) being present in amount of from 0 to 25 mol percent of the amount of units (a), and from 0 to 15 mol percent of the total copolymer,

units in amount of at least 5 mol percent of the total copolymer,

| xii-Q3103 and :dQsro 1 1 units in amount such that the total number of units of the formula in said copolymer is from 1 to 15 mol percent of the total copolymer and (5) ZSiO units in amount of from to 10 inclusive mol percent of the total copolymer, said units being interconnected through SiOSi linkages, in which R is selected from the group phenyl, methyl and radicals,

Q is selected from the group consisting of hydrogen and C F CH CH n is an integer from 1 to 8 inclusive,

R and D are each independently selected from the group consisting of phenyl and methyl radicals, at least one R and D group per silicon being on the average a methyl radical,

R' is selected from the group consisting of methyl and phenyl radicals,

Q is selected from the group consisting of phenyl,

methyl and radicals, X is selected from the group consisting of chlorine and bromine, a is an integer from 1 to 4 inclusive, and b has a value from 0 to 2 inclusive. 9. A method of lubricating moving metallic parts which comprises maintaining therebetween a copolymer having (1) trimethylsiloxy units on the ends of the molecules,

the remaining units in said copolymer being substantially all (2) dimethylsiloxy units in amount of at least 24 mol percent,

ltl/lez Bile:

units in amount of not more than 25 mol percent of the amount of (2) and not more than 15 mol percent of the total copolymer,

(4) trifluoropropylmethylsiloxy units in amount of at least 5 mol percent of the total copolymer and (5) dichlorophenylsiloxane units in amount of from 1 to 15 mol percent based on the total copolymer.

References Cited UNITED STATES PATENTS 2,599,984 6/1952 Fletcher et a1 260448.2 2,809,207 10/ 1957 Gainer 260448.2 2,894,969 7/1959 Pierce 260448.2 2,961,425 11/1960 Pierce et al. 260448.2 3,050,492 8/1962 Polmanteer et al. 260448.2 3,061,545 10/1962 Badger 252-49.6

FOREIGN PATENTS 1,225,228 2/1960. France.

TOBIAS E. LEVOW, Primary Examiner.

SAMUEL H. BLECH, Examiner.

P. F. SHAVER, Assistant Examiner. 

1. AS A LUBRICANT A COPOLYMER HAVING (1) UNITS OF THE GROUP CONSISTING OF 